This invention relates to valves for use with vessels containing gas under pressure, and more particularly to a crashworthy solenoid actuated valve for use in compressed natural gas powered vehicles.
Because of environmental concerns and emissions laws and regulations, manufacturers of motor vehicles are searching for a clean burning and cost efficient fuel to use as an alternative to gasoline. Natural gas is one candidate for such a purpose, and many vehicles have been converted to natural gas as a fuel source. Typically, the natural gas is stored on board the vehicle in compressed form in one or more pressurized cylinders.
Valves which control the supply of compressed natural gas (CNG) to the engine of a vehicle are exposed to large variations in environmental conditions. For example, wide variations in temperatures may be encountered. This variation in temperature may result in the nominal working pressure in a gas cylinder to vary several hundred up to a few thousand pounds per square inch (psi). Thus, the control valve must be able to handle high gas pressures without failure.
Further, in the event of a crash, the gas valve must not fail in an unsafe or catastrophic manner. Additionally, it is desirable that the valve close automatically in the event of an electrical failure or indication of a crash.
Grant et al, U.S. Pat. No. 5,188,017, teaches a natural gas cylinder fitting and solenoid valve which can be used to control the flow of CNG from a pressurized source to an engine of a vehicle. Both externally-mounted and internally-mounted embodiments are shown. Internal mounting of the valve within the pressurized cylinder provides additional protection from a crash. Wass et al, U.S. Pat. Nos. 5,193,580 and 5,197,710 also teach internally-mounted, solenoid controlled gas valves for use in CNG powered vehicles. The U.S. Pat. No. '580 patent also includes a manual override feature which can be used to block the flow of compressed gas from the cylinder to a gas line.
However, while the Grant and Wass valves are stated to be crash resistant or crash proof, in the event of an accident which causes the exposed portions of the valves to be sheared off from the neck of the pressurized gas cylinder, the valves would not be able to block the flow of gas out of the cylinder as the inlet, outlet, and electrical feed through connections all communicate with the gas in the cylinder. Accordingly, there remains a need in this art for a crashworthy solenoid actuated valve for CNG powered vehicles which will automatically block the flow of gas out of a cylinder to a gas line in the event of an electrical failure or crash and which will not fail catastrophically in the event of a crash. Further, there remains a need for such a valve which can withstand high pressures without leakage over a range of temperatures.